A multicore optical fiber preform having a plurality of core portions each extending in a predetermined axial direction can be manufactured by the rod-in-collapse method (cf. Patent Literatures 1 and 2). In the rod-in-collapse method, first, a glass body of a nearly circular cylinder shape is perforated to form a plurality of holes extending along a central axis of the glass body, thereby producing a glass pipe. Subsequently, a plurality of core rods each including a core portion are inserted into the respective holes of the glass pipe and the glass pipe is heated with the plurality of core rods being inserted in the respective holes, thereby to implement integration of the plurality of core rods and the glass pipe. The multicore optical fiber preform is manufactured through the above rod-in-collapse method.
A multicore optical fiber can be manufactured by drawing the multicore optical fiber preform manufactured as described above.